Solid state contactor with improved interconnect structure

ABSTRACT

A printed circuit board for selectively communicating power from a power source to a use has an input bus for receiving a power supply. A transistor is connected to the input bus and is positioned on one side of the input bus in a first direction. An output bus is connected to the transistor on an opposed side of the transistor relative to the input bus. The transistor is intermediate at the first input and output buses in the first dimension. A power supply system is also disclosed.

BACKGROUND OF THE INVENTION

This application relates to an improved printed wiring board forcommunicating a power supply to a use.

The control of electronic components is becoming increasinglysophisticated. One common application is a printed wiring board whichincludes a power supply communicating power through an input bus. Aplurality of switches, typically transistors, and in many cases, metaloxide semiconductor field-effect transistors (MOSFETs) communicate theinput bus to an output bus. A control board controls operation of aplurality of MOSFETs to selectively transmit power from a power sourceto various uses.

There are a plurality of such boards utilized on most aircraft, and alsoin other aerospace applications.

In the known art, the input bus and the output bus have been positionedin a common plane. The MOSFETs are mounted on one of the buses, andconnected to the other by wires. This has required a relatively largeamount of space between fingers on the input and output buses, and hasthus resulted in the overall arrangement being undesirably large.

SUMMARY OF THE INVENTION

A printed circuit board for selectively communicating power from a powersource to a use has an input bus for receiving a power supply. Atransistor is connected to the input bus and is positioned on one sideof the input bus in a first direction. An output bus is connected to thetransistor on an opposed side of the transistor relative to the inputbus. The transistor is intermediate at the first input and output busesin the first dimension. A power supply system is also disclosed.

These and other features may be best understood from the followingdrawings and specification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a power supply system.

FIG. 2 is a top view of the system.

DETAILED DESCRIPTION

FIG. 1 shows a power supply system 20 incorporating a printed wiringboard 21. A power supply 22 selectively provides power to an input bus24. It should be noted that FIG. 1 shows only one portion of the wiringboard 21, and the wiring board would actually have a plurality of thestructure shown in FIG. 1, and as perhaps better shown in FIG. 2. Theinput bus 24 is connected to a transistor 26 which may be a MOSFET. Anencapsulant 27 encloses the area around the MOSFET 26. A controller 28controls the transistor 26. A body 30 mounts all of the structure.

It should be understood that control circuitry 28 (See FIG. 2) isincorporated somewhere within the body 30. A spacer 32 may be formed ofAlN or Al₂O₃ or other appropriate materials. Spacer 32 separates anoutput bus 34 from the body 30. A die attachment 35 may connect thetransistor 26 to the input bus 24. The output bus 34 communicates with ause 36, which may be a use on an aerospace application.

In fact, the overall system such as shown in FIG. 2 may have a pluralityof transistors (or MOSFETs) 26, and could communicate with a pluralityof uses.

The operation of the control circuit and when it would be desirable totransfer power is known in the art. It is the architecture of theprinted wiring board 21 which is novel to this disclosure.

As can be appreciated, the printed wiring board 21 extends along adimension X and along a dimension Y in the illustrated plane. In theprior art, the buses 24 and 34 would be co-planer in the dimension X. Inthe prior art, MOSFETs are electrically connected to the bus bars bywire-bonds. However, as can be seen, they are spaced within the X planein this disclosure. They also overlap within the dimension Y, which isperpendicular to the dimension X. That is, a portion 37 of the outputbus 34 is positioned on an opposed side of a solder joint 38 connectingthe transistor 26 to the bus 34 relative to the input bus 24. Thetransistor 26 is, thus, also positioned intermediate the portions 37 anda portion 39 of the input bus 24 on an opposed side of the solder joint38 and transistor 26. For each MOSFET connection to the bus bar, therewill be multiple solder joints such as greater than two and as many aseight or more.

FIG. 2 is a view generally looking downwardly on FIG. 1. It should beunderstood that FIG. 1 only illustrates a portion of FIG. 2. As can beseen, input bus 24 actually has a plurality of fingers 42 which areinterspersed with fingers 40 from the output bus 34. The portions 39 and37 overlap in the Y dimension, which is perpendicular to the Xdimension. Spaces 52 exist between fingers 42 and beneath finger 40.Similar spaces 53 between fingers 40 are above a finger 42. That is,fingers 40/42 span spaces 52/53. With this arrangement, the density ofcomponents within the printed circuit board is increased and the overallsize can be decreased. As can also be seen, the fingers 42 are spacedfrom each other in the Y dimension, and the fingers 40 are also spacedfrom each other in the Y dimension.

The disclosure could be summarized as describing a printed circuit board21 that selectively communicates power from a power source 22 to a use36. An input bus 24 receives the power supply from source 22. Atransistor 26 is connected to input bus 24 and positioned on one side ofthe input bus in a first direction. An output bus 34 is connected totransistor 26 on an opposed side of the transistor 26 relative to inputbus 24. Thus, transistor 26 is intermediate the input and output busesin the first dimension. Due to direct solder interconnect, spacingbetween the bus bars can be reduced. This results in reduction of busbar width for a given current. Due to direct solder interconnect, morebus bars can be packaged. This reduces heat load. This improves thermaldesign. For example, current flow per bus bar can be reduced by 33%compared to a prior art printed wiring board.

Although an embodiment of this invention has been disclosed, a worker ofordinary skill in this art would recognize that certain modificationswould come within the scope of this invention. For that reason, thefollowing claims should be studied to determine the true scope andcontent of this invention.

The invention claimed is:
 1. A printed circuit board for selectivelycommunicating power from a power source to a use comprising: an inputbus for receiving a power supply; a transistor connected to said inputbus and positioned on one side of said input bus in a first dimension;an output bus connected to said transistor on an opposed side of saidtransistor relative to said input bus, such that said transistor isintermediate said input and output buses in said first dimension, andsaid input and output buses having portions overlapping each other in asecond dimension which is perpendicular to said first dimension; andeach of said input and output buses include a plurality of fingers withsaid fingers having portions overlapping each other in said seconddimension and other portions which overlap a space between the fingersof the other of said input and output buses, the fingers on said inputbus being spaced from each other in said second dimension, and thefingers on said output bus being spaced from each other in said seconddimension.
 2. The printed circuit board as set forth in claim 1, whereina die attachment is utilized to connect said transistor to one of saidinput and output buses and a solder joint is utilized to connect thetransistor to the other.
 3. The printed circuit board as set forth inclaim 1, wherein a spacer is positioned between said output bus and saidprinted circuit board.
 4. The printed circuit board as set forth inclaim 1, wherein said transistor is a MOSFET.
 5. A power supply systemcomprising: a source of power, a printed circuit board for controllingthe supply of power from said power source to a use, said printedcircuit board including an input bus for receiving power from said powersupply; a transistor connected to said input bus, and positioned on oneside of said input bus in a first dimension; an output bus connected tosaid transistor on an opposed side of said transistor relative to saidinput bus, such that said transistor is intermediate said input andoutput buses in said first dimension, and said input and output buseshaving portions overlapping each other in a second dimension which isperpendicular to said first dimension; and each of said input and outputbuses include a plurality of fingers with said fingers having portionsoverlapping each other in said second dimension and other portions whichoverlap a space between the fingers of the other of said input andoutput buses, the fingers on said input bus being spaced from each otherin said second dimension, and the fingers on said output bus beingspaced from each other in said second dimension.
 6. The power supplysystem as set forth in claim 5, wherein a die attachment is utilized toconnect said transistor to one of said input and output buses and asolder joint is utilized to connect the transistor to the other.
 7. Thepower supply system as set forth in claim 5, wherein a spacer ispositioned between said output bus and said wiring board.
 8. The powersupply system as set forth in claim 5, wherein said use is in anaerospace application.
 9. The power supply system as set forth in claim5, wherein said transistor is a MOSFET.